Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field.
Liquid crystal on silicon (LCOS) based wavelength selective switches (WSS) have been developed based on highly stabilized optical trains. In a push for minimizing the height (profile) of WSS components (single-slot applications) there is a requirement to reduce the stability and thermal shielding of the components.
Previous known approaches introduce an optical inversion into the optical system to maintain the required stability over temperature and mechanical aberrations. However, these approaches have not been able to be scaled to higher functionality devices such as dual devices or high port count devices.
One suggested approach is to look at using the ability of the LCOS device to readjust and steer the light to overcome the change in alignment. However, this is problematic because it changes the image of the LCOS, giving rise to problems such as:                Transient changes to the port isolation which can be poorly controlled.        Difficulties in ensuring calibrations are valid across all operating conditions.        Significant variations in the orders of the switching and attenuation images occur as alignment changes, so an uncontrolled order may emerge as a port isolation issue.        